B i.e. Acute psychosis- Delusions or hallucinations (suchas hearing voices in this case) with grossly disorganized speech and behavior (such as muttering to self, gesticulation, aggressiveness in this case) of acute onset with normal cognition & consciousness indicate the diagnosis of acute psychosis (i.e. psychosis of acute onset). This acute psychosis may be d/t psychotic disorder d/t general medical condition (such as high fever as in this case) or d/t brief psychotic disorder (DSMIVTR), or d/t acute and transient psychotic disorder (ICD-10). So here the term acute psychosis is used to depict the clinical picture not the cause of that clinical picture.Delirium can also present acute onset disorganized behavior (agitation) and speech (incoherent) with delusions or hallucinations but the delusions are poorly elaborated & transient, the course of disease is fluctuant (eg sun downing). And characteristically there is clouding of (disturbance in) consciousnesss (i.e. reduced clarity of awareness of the environment) and disorientation (change in cognition) in delirium. Just like psychosis clinical picture of delirium may also be d/t various reasons such as general medical condition / substance intoxication/ withdrawal.- Dementia is a chronic slow/insiduous process presenting with decrement in intellectual abilities (such as sho & long term memory, judgement, abstract thinking, impulse control, personal care and personality)Q.- Delusional disorder presents with nonbizarre delusions (involving situations that occur in real life) of at least 1 months durationQ. Apa from the impact of delusion (s) or its ramifications, functioning is not markedly impaired and behavior is not obviously odd or bizarre (i.e. criteria. A of schizophrenia has never been met). However, tactile or olfactory hallucinations may be present if they are related to delusional theme.